Field of the Invention
The present invention relates to an inertial drive actuator.
Description of the Related Art
An actuator which displaces a drive shaft in an axial direction by supplying a saw-tooth wave drive pulse to an electromechanical transducer element fitted to a drive shaft, and moves a movable member which is friction-fit to the drive shaft in the axial direction, has been known. Hereinafter, such an actuator will be called as an ‘inertial drive actuator’. Such inertial drive actuator is proposed in Japanese Patent Application Laid-open Publication No. 2009-177974, for example.
In a conventional inertial drive actuator, one end of a piezoelectric element is fixed to a fixed member, and the other end of the piezoelectric element is fixed to one end of a vibration substrate. A movable body which is movable in a direction of vibration of the piezoelectric element is disposed on the vibration substrate. Here, the fixed substrate or the vibration substrate is made of a magnetic material (such as iron, and stainless steel having a magnetic property), and an adsorbing portion is also a magnetic material. When an electric current is applied to a coil, a magnetic field is generated. The magnetic field that is generated also generates a magnetic field in the adsorbing portion. Due to the magnetic field generated in the adsorbing portion, a magnetic adsorptive force is generated in the vibration substrate or the fixed member which is a magnetic material, and as a result of which, the movable body and the vibration substrate make a close contact, and a frictional force is generated between the movable body and the vibration substrate.